Seattle is enjoying one of its all-too-rare episodes of snow—well, I’m enjoying it, at least. Upon leaving the house this morning to walk to work, I found the sidewalks lightly dusted with an interesting type of snow we in the biz call graupel.

Most snowflakes, the six-sided ones you probably think of when you think of “snowflake”, grow by the condensation of water vapor. The individual water molecules attach to the snowflake in an orderly fashion, like building a structure out of Legos, and you end up with a regular crystalline shape.

Sometimes, though, the snowflake will pass through a cloud of water droplets as it falls down to the ground. As it hits the snowflake, the whole water droplet will freeze almost instantly, retaining its rounded shape. The snowflake bounces around in the cloud of water droplets, accumulating more and more, and your orderly Lego structure starts to look like someone has been pelting it with spitballs. These frozen water droplets are called rime. When so much rime has accumulated that the underlying shape is no longer visible, the snowflake has become a pellet of graupel.

In the picture below (sorry for the questionable quality, it’s a cell phone camera) you can see quite a few snowflakes; I’ve circled one on the left that retains the crystalline snowflake shape, and one on the right that’s still clearly six-sided, but so covered in rime it looks like it’s wearing a fur coat. (My advisor called this a “textbook” rimed snowflake.) Elsewhere in the picture you can see a few pellets of shapeless graupel.

Circled on the left: a classic snowflake. Circled on the right: a snowflake covered with rime (frozen water droplets.)

Incidentally, this also goes to show that you don’t need a microscope to appreciate snowflakes; your eyes will do just fine. I’ve found that a good method is to go out when the snow is falling and catch snowflakes on a fuzzy hat, either faux fur or knitted with especially fuzzy yarn; the snowflakes will be caught on the fibers, where they can be more easily examined without melting.

One of the things I find interesting about ice is its use in engineering. Ice and snow are actually fantastic building materials for certain purposes–mostly due to their cheapness and ubiquity, but sometimes also because they have useful physical properties. You may have heard of Pykrete, the mixture of ice and wood pulp that was proposed as a potential material for aircraft carriers. The wood pulp increased the strength of the brittle ice; it also reduced its thermal conductivity, slowing down melt. But apparently the fact that ice flows under its own weight, combined with the fact that such a carrier could only be used in cold weather or with massive refrigerating apparatus, doomed the project.

Ice structures needn’t be solely functional. For one thing, it’s a popular sculptural medium. You’ve also probably heard of ice hotels like this one in Sweden or this one in Québec. Despite its beauty, though, ice isn’t the most functional material for living quarters; it conducts heat too well. For dwellings, you want something with good insulative properties: snow!

The most famous snow dwellings are those made by the Inuit people of the high Arctic: igloos. (“Iglu” can actually refer to any type of dwelling, but for my current purposes I’m most interested in the temporary, dome-shaped, snow-and-ice structures.) This webpage discusses igloo technique, including the use of lamps to melt the interior so that it will refreeze as structurally stronger ice. (It is worth noting that traditional cut-block igloos work best with a certain type of wind-packed dry snow that is, I think, much easier to find in the Arctic and Antarctic than in temperate regions.)

But snow shelters are useful for anyone camping in snowy conditions. This chapter of the US Antarctic Program Field Manual (PDF link) describes the basics of several different types of snow shelter. The quinzhee, for instance, used to be a major feature of McMurdo Happy Camper school. The US Antarctic Program approach is to build up the quinzhee by shoveling snow on top of a pile of equipment which is then removed to create a cavity; more traditional quinzhees may involve creating a pile of snow and later hollowing it out.

When I did Happy Camper they emphasized the snow trench as a shelter that could more easily be built by one person, if necessary:

Snug and warm(ish.)

The one disadvantage of a snow dwelling this small is that one is forever knocking snow off the walls and down the back of one’s neck. Igloos and quinzhees are far preferable if you have the time and manpower, not to mention being more visually impressive.

“The wind came back today. It started out calm enough, and we almost went out to make measurements. But when we called the forecasters at McMurdo, they told us that the wind was due to pick up soon, and would get to thirty knots–gusting to fifty–sometime tomorrow.

On hearing this, Mel pointed out that we were going to need to prepare the camp for the onslaught of wind and drifting snow. This meant building another snow wall.

A snow wall is both made of snow and designed to control snow. It’s simply a low structure made of snow blocks that serves to slow down the wind and make it drop its snow upwind of camp, instead of on top of us. The wind carries truly impressive amounts of drifting snow across the landscape, and it dumps it every time it gets slowed down by passing over irregularities, such as our tents. We already have two snow walls, but in the six weeks the camp has been here, the space behind them has already entirely filled with drifted snow.

A snow wall with the space behind it filled in with snow.

Most of the snow around here is extraordinarily hard-packed, and our resident snow scientists are astonished by its strength-to-weight ration. In many places, you need a chainsaw to really make much of a dent in it in any sort of efficient way. So, Mel got out the chainsaw, and cut enough blocks to make our walls.

Sorry, no chainsaw pics--this is after it gave out and Mel and Martin were cutting out the last few blocks by hand.

We had them assembled in fairly short order, so we got a little creative. Mel built an arch, I built a turret, and Martin and Ruschle spent most of the afternoon digging a snow pit and being astonished at it.

Blocks en route to their place in the wall.

Mel's arch and flowerpot (or rooster, depending who you ask.)

Martin says the snow here consists mostly of depth hoar, a sort of re-crystallized snow that’s ordinarily [that is, in more temperate regions] light and crumbly, but here is very hard—“like cement”, he says. Ordinary snow shovels would break on the first try. We use sturdy metal gardening shovels (the labels say they’re “contractor grade”) and they still have trouble. The depth hoar snow is also full of little crystalline cups and ??, quite delicate-looking for all its strength.

So, we have a new snow wall, and hopefully we’re well prepared for the coming storm. I’ll let you know how it goes. Cheers!”

Speaking of timelapse videos, here are a couple of others that I quite like:

Sea ice near an Adelie Penguin colony. Shows the evolution of sea ice over a period of time (perhaps late spring and summer?) Partly I just like this because the motion of the tides makes it look like the ice is breathing.

I’ve been trying to do more with this blog than just write text and post it—WordPress offers a wide variety of features, and blogging is at its best when it’s part of a larger ecosystem rather than just one person talking in isolation. So I’ve been adding links to the blogroll. Allow me to present a few here:

From a Glacier’s Perspective offers detailed descriptions of glacier retreat around the world, with each post focusing on a different glacier. This post describes how a glacial feature called ogives can be used to help measure glacier velocity. (Ogives are “ripples” in the glacier that form due to the influence of icefalls: the area of ice that happens to be going over the icefall during the summer melt season melts faster than the ice around it, leaving a trough that then moves down the glacier.)

The IceBridge Blog recounts news from NASA’s IceBridge Campaign. The aerial surveys of IceBridge use a variety of instruments–lasers, radar, even a gravimeter–to survey the Earth’s ice. The information gathered from IceBridge will “bridge” the gap between IceSAT-1, which stopped taking data in 2009, and IceSAT-2, which is scheduled for launch in 2016. The blog includes both pretty pictures of icy landscapes and discussions of the science behind the work, such as this post on how airborne gravimetry can tell us about the shape of the land below water and ice.

For those of you wanting to see more of Antarctica (one of my favorite continents!) there’s the “Landsat Image Mosaic of Antarctica (LIMA)” which allows you to pan and zoom all over the continent. Anthony Powell’s photography shows the place on a slightly more intimate scale, mostly around McMurdo and including some justly famed timelapse films. Or Maria Coryell-Martin’s Expeditionary Art captures both the Antarctic and the Arctic, capturing the feel of the icy realms in a way photographs sometimes can’t.

I’ll be adding more as time goes along! In particular, I want to find some good resources on ice elsewhere in the solar system, which is a fascinating subject I haven’t even gone into yet.

Oneof the tricky bits about glaciology is distinguishing between different ice features. There’s the question of terminology, such as figuring out when an icefield (a large mass of glacial ice, often with many glaciers flowing out of it) becomes an ice cap (same thing, but larger and tending to be dome-shaped) becomes an ice sheet (like an ice cap, but over 50,000 square kilometers.) Today my dad (happy Father’s Day!) alerted me to an article in the Anchorage Daily News discussing the difficulties of counting glaciers.

Glaciers, like rivers and streams, often flow into each other or split apart. Exactly when one glacier becomes two glaciers can be a tricky thing to determine, and now that so many glaciers are retreating, these points of merging or splitting may disappear altogether. So what was one glacier with three branches might become three glaciers. For instance, in the photo below you can see how several tributaries merge into a single calving front at Columbia Glacier.

And here’s an amazing timelapse video from the Extreme Ice Survey (I’ve seen it shown at a lot of glaciologist meetings and conferences) that shows how the front of Columbia Glacier retreats back until the several “tributaries” start to look like separate glaciers again. It goes so far and so fast they have to move their camera several times so that the front of the glacier stays in the frame.

Of course, for many purposes, the important thing is not how many glaciers there are, but how much ice there is in the glaciers. Although there’s not very much water stored in mountain glaciers like these compared to the water stored in the great ice sheets of Antarctica and Greenland, the mountain glaciers are melting extremely quickly (well, quickly by glacial standards) so a major percentage of current sea level rise is due to meltwater from glaciers like the Columbia. You can’t tell how thick a glacier is just by looking, so determining the volume of the world’s glaciers—and just how fast that volume is changing—is one of the important ongoing problems in glaciology.

A scanning electron microscope image of cells of Chaetoceros dichaeta, a type of diatom, from Cefarelli et al. 2011.

One of the most interesting aspects of climate dynamics is the role of feedbacks. There are two kinds of feedbacks, positive and negative. This earlier post about Snowball Earth describes a positive feedback, in which Effect One (the freezing of seawater) leads to Effect Two (the reflection of light back into space, which cools the planet) which in turn intensifies Effect One (more seawater freezes.) You can see a positive feedback effect at work in a more familiar environment when there’s a run on a bank: Effect One (the bank looks like it might fail) leads to Effect Two (depositors rush to get their money out of the bank) which strengthens Effect One (the bank, bleeding cash, now looks like it’s in even more trouble.) Positive feedbacks tend to make a system unstable. So they’re not really all that positive in the conversational sense of the word; in most systems, you want to avoid them.

This post, on the other hand, describes the carbonate weathering cycle–a negative feedback effect. In negative feedback, Effect One (warming of the planet from CO2) leads to Effect Two (weathering speeds up, removing CO2 from the air more quickly) which damps down Effect One (with less CO2, the planet cools down again.) Negative feedbacks make systems more stable.

Climate is an incredibly complicated system, with many feedbacks both positive and negative. This article at Science News, Melting icebergs fertilize ocean, describes the discovery of yet another one.

Living things in the ocean are limited by available nutrients, including iron. Some people think we should deliberately dump iron in the ocean to spur the growth of plankton that will suck CO2 from the atmosphere as they grow and then seal it away on the ocean floor when they die and sink to the bottom. Of course, many other people think that this is likely to have a lot of unintended consequences if we do enough of it to make a dent in atmospheric CO2.

But it turns out that icebergs in the Weddell Sea are already doing this, on a smaller scale. Glacier ice has a lot of iron in it compared to seawater, probably due to a combination of dust collected from the atmosphere and sediment from underneath the glacier. When icebergs break off the glacier and melt in the ocean, that iron is released, and thriving communities of algae and plankton spring up around the bergs. The more the planet warms, the faster glaciers flow and the more icebergs end up in the sea; the more icebergs there are, the more carbon gets soaked up by sea life, slowing down warming a little bit.

This effect is probably small compared to other feedbacks that are part of climate change, and it’s not very helpful from a human perspective, since each melting iceberg contributes to rising sea levels. But it’s always interesting to discover a new cog in the great machine of the Earth.

Hey guys! I wrote you a song! It’s about the epic tale of survival that resulted from Shackleton’s attempted Trans-Antarctic Expedition; I used this website as a reference for some of the events, or you could read Shackleton’s own book on the experience, South. Be sure to check out the pictures, which are widely and deservedly regarded as the best part of the book.

‘Twas early in the century
The world prepared for war
But Shackleton intended the Antarctic to explore.
Some men sail for profit
Some sail for renown
But this one sailed for Science and the glory of the Crown.

Through the icebergs that clash, through the great waves that roll,
The mighty ship Endurance went a-sailing for the Pole.

The whalermen had warned them
That the ice would be severe
They were still above the Circle when the first floes did appear
Still bravely they sailed southward
But soon they were beset
Imprisoned in the heaving ice, but not defeated yet

Through the icebergs…

They whiled away the winter
Drifting ‘cross the Weddell Sea
When finally the sun arose, they thought they’d soon be free
But the mounting pressure of the ice
Was more than she could bear
In just days the stout Endurance was crushed beyond repair

Through the icebergs…

They loaded up the lifeboats
With provisions piled high
They watched her sink beneath the ice as, helpless, they stood by
The men camped on an icefloe
Let it take them where it would
It brought them near an island before breaking up for good.

Through the icebergs…

The isle was cold and barren
Inhospitable to man
So Shackleton devised another daring rescue plan.
He’d sail eight hundred miles
‘Cross the world’s most stormy sea
To the whalers on South Georgia he would make his earnest plea.

Through the icebergs…

A thousand times the pounding waves
Near sank the tiny boat
They lost most of their gear and food, yet somehow stayed afloat
When the party reached South Georgia
Thirst-tormented and sore
They realized the whaler-camp was on the further shore.

Through the icebergs…

They scaled the craggy mountains
And crossed crevasses deep
They stumbled into whaler-camp half-crazed from lack of sleep
The whalers were astonished
When these strange men came in view
Soon Shackleton secured a ship to rescue all his crew

Through the icebergs…

Let Shackleton’s Antarctic fame
For centuries survive
For with all their trials and troubles, every man came back alive!

Not much time–heading to the airport soon to wing my way home to Seattle–but here are some nice pictures of ice sections, the things I spent long long hours in the cold lab working on. I’ll talk more about the process, and their scientific importance, soon.

Vertical section, from around 10 cm below the surface.

Same section between crossed polarizers to show some of the crystal structure.

Larger, more clearly defined crystals in a horizontal cross section of the core.

Also, because everyone likes charismatic megafauna, here is a Svalbardian reindeer! (“Reindeer” in English means a domesticated caribou, but the Svalbard ones are wild.)

The first order of business is to actually get to the field site, Tempelfjorden. It’s around fifty or sixty kilometers (thirty to thirty-five miles) away from Longyearbyen by snowmobile, which is the conveyance of choice. Snowmobiles have numerous benefits: they’re fast, they can pull good-sized sleds full of equipment, they can deal with a wide range of snow and ice conditions, and they’re loud enough to repel polar bears.

The trip out takes one-and-a-half to two hours, depending on the light and snow conditions; for instance, it’s more difficult to drive fast on days with cloudy, diffuse light because snow features become very hard to see. It’s quite the scenic commute, although snowmobiling is more physically draining than you might expect if you’re not used to it. We arrive around 11 AM, if we’ve planned things right.

Time for a photo break.

Once we get to Tempelfjorden, Bonnie and SvalSteve select a good site for taking measurements–mainly they want something that’s not too close to well-traveled snowmobile routes, since Tempelfjorden is actually a reasonably popular tourist destination. (I discovered yesterday that there are actually daily snowmobile tours out there; it’s kind of cheering to find out that your field site is someplace people pay to go to. And the tourists only spend about eight hours on the roundtrip, but we get to be out doing science for THIRTEEN hours!) Once it’s selected, we get to work putting together the equipment.

Not scientific equipment, but nevertheless important, given that it's difficult to take sea ice measurements from inside a polar bear.

This has been an ambitious trip in terms of the number of measurements we’re trying to take on each day out. We measure snow and ice albedos, using a piece of equipment somewhat similar to the one I’ve used in Antarctica, only smaller and more portable (currently set up so it can be mounted in the Backpack of Science, of which I have a picture around here somewhere.)

Bonnie and Naomi take albedos of the bare ice.

We measure the transmission of light through the ice using several instruments mounted on two different arms, Bonnie’s and SvalSteve’s.

Bonnie's arm. When it's underwater, the foam makes the lower part float upwards so that the instruments are right under the ice, some distance from the hole.

SvalSteve and colleague Mats carrying their arm. It has two different instruments, one for general transmitted light and one for transmitted UV radiation.

We drill a hole through the ice to make a detailed profile of the light at each level within it.

Naomi calibrating the profiler.

We make ice cores to be melted and filtered a few different ways and additional cores to slice thin and put under the microscope.

SvalSteve drills a core the fast way, with a motor.

We dig snow pits (to measure profiles of snow characteristics such as density) and take snow samples so we can melt and filter those too.

SvalSteve and Naomi work on a snow pit.

Phew. By the time we’re done with all of that and have packed away all the equipment, it’s late in the day, and we generally get back to Longyearbyen just in time to rush to a local restaurant before they stop serving food at 11 P.M.

Next: more about how all that equipment actually works, and what we get up to in the lab!